feat: remove global mediator commands from Web IDE

Issue: Remove global mediator command initialization f... (#469 - closed)

What does this MR do and why?

As we prepare to upgrade VSCode fork to 1.94.0, we want to remove global mediator commands from the Web IDE:

• It is not secure and is scheduled to be removed now that OAuth is fully enabled in the Web IDE.
• It relies on the VSCode buffer module, which is no longer included in the VSCode artifact starting 1.94.0.

Changes include:

• Remove commands from the workbench config upon VSCode bootstrap– we no longer want to register commands when there is no authProvider. Also remove now unused references to bufferModule.
• Remove None auth type option from the Example App. This auth type option relies on global mediator commnands to read files in the project, for example. The default option is now oauth.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Recording	Notes
1	No None Auth type option in the Example App config form Can read files No regressions on GitLab Workflow extensions: DuoChat and Code Suggestions work as expected
2	List of branches in project are loaded Can switch branches Changes are committed successfully.

How to set up and validate locally

• Pull this branch and run yarn start:example in the gitlab-web-ide project